Is the initiation of glaciation on Antarctica related to a change in the structure of the ocean?

Evidence from ocean drilling suggests that the glaciation of East Antarctica began at the Eocene-Oligocene boundary, but took time to spread over the entire continent. The presence of calcareous nannoplankton in the Arctic basin prior to the Oligocene and their absence thereafter suggests that the ice cover of the Arctic Ocean also developed at the Eocene-Oligocene boundary. Both events appear to be related to the development of the modern oceanic structure, but it remains uncertain whether the ocean changed in response to the development of ice covered polar regions or vice versa.